Abstract The cerebral cortex consists of 2 hemispheres, the left and the right. These are divided by the falx cerebri, a dural-derived structure. The cerebral cortex receives input from various subcortical structures, often connecting through the thalamus and from other areas of the cortex by association fibers. The cortex then projects back to wide regions of the central nervous system, including the cortex, thalamus, basal nuclei, cerebellum, brainstem, and spinal cord. The types of fibers connecting areas of the central nervous system are designated according to the regions they connect. For instance, the fibers connecting the cortex to subcortical structures are called projection fibers. The fibers connecting 1 hemisphere to the opposite hemisphere are called callosal fibers, and the fibers connecting areas within the same hemisphere are called association fibers. Fibers connecting the cortex to the thalamus are designated corticothalamic fibers.